Device for driving the thread out of the way from under the presser foot of a sewing machine

ABSTRACT

A METHOD FOR DRIVING OFF THE NEEDLE THREAD FROM A SEWING MACHINE HAVING A CUTTING MECHANISM FOR THE NEEDLE-THREAD AND THE HOOK THREAD IS DISCLOSED, CONSISTING IN PROJECTING AN ENERGETIC STREAM OF COMPRESSED AIR FROM BENEATH THE UNDERSIDE OF THE PRESSER FOOT. THE DEVICE FOR PERFORMING THE METHOD ESSENTIALLY COMPRISES A PROPERLY ORIENTED AIR DUET, FED BY A COMPRESSED AIR   SOURCE. THE AREA WHERE THE AIR-STREAM DRIVES THE THREAD IS NEVER CRITICAL AND THE DEVICE IS EXTREMELY SIMPLE AND ABSOLUTELY RELIABLE.

Oct. 26, 1971 c, QNT| 3,614,935

DEVICE FOR DRIVING THE THREAD OUT OF THE WAY FROM UNDER THE PRESSER FOOT 0F A SEWING MACHINE Filed April 9, 1969 INVENTOR @Z/ FA V ATTORNEY United States Patent Cl, 1122 18 R 1 Claim ABSTRACT OF THE DISCLOSURE A method for driving off the needle thread from a sewing machine having a cutting mechanism for the needle-thread and the hook thread is disclosed, consisting in projecting an energetic stream of compressed air from beneath the underside of the presser foot. The

' device for performing the method essentially comprises a properly oriented air duct, fed by a compressed air source. The area where the air-stream drives the thread is never critical and the device is extremely simple and absolutely reliable.

This invention relates to a method and a device for driving away the thread of the needle of a sewing machine.

It is known that in the sewing machines which are equipped with an automatic thread cutting device, both for cutting the thread coming from the needle and that coming from the hook, it is imperative to prevent the needle-thread from being pinched beneath the presser foot as the latter is depressed when preparing for a new seamline. It is also known that both the mechanical and electromechanical devices hitherto adopted for that purpose have an intricate and expensive constructional arrangement which, regrettably, is also somewhat unreliable in service. In addition, the fact of acting when the presser foot is being lowered is extremely dangerous, since the needle becomes liable to breakage. Exactly for the latter reason, all the known devices for driving the thread out of the way of the needle, were invariably caused to act during the lifting stroke of the presser foot.

The principal object of the present invention is to provide means for driving out of the way the needle-thread of a sewing machine, equipped with an automatic cutting mechanism for the needle-thread and the hook-thread, comprising a stream of compressed air positioned to be effective in the immediate vicinity of the needle and the presser foot, and operative before the presser foot has been completely depressed into contact with the fabric, to impart to the thread a thrust so as to drive the needlethread away from beneath the underside of the presser foot.

Preferably, but not compulsorily, the stream of compressed air which is intended to drive the needle-thread from beneath the underside of the presser foot is caused to emerge from an opening formed through the underside of the presser foot itself.

The device for reducing the inventive method to practice essentially comprises: a source of compressed air, a duct leading from said source to a point in the immediate vicinity of the needle and the presser foot, said duct being oriented so that the air stream emerging from the duct impinges onto the needle-thread in such a direction as to drive it away from beneath the underside of the presser foot.

According to a preferred embodiment of the device intended to reduce the inventive method to practice, the presser foot has a slanting through-bore which opens at the underside of the presser foot and is connected, at its top end, to a pipe fitting to which an appropriate hose is connected, and which receives compressed air fed from an appropriately arranged source.

It should be observed, in connection with said source, that already a few sewing machines are equipped with a pneumatic actuating device for the presser foot. Inasmuch as, as outlined above, the present invention provides for feeding compressed air before the presser foot has been completely lowered onto the fabric being processed, it is obvious that the generation of the compressed air jet intended to drive the needle thread away from the presser foot should be properly timed with the lowering stroke of the compressed air ram which causes the movement of the presser foot to occur.

In the light of the foregoing, the invention will be better illustrated in connection with a preferred embodiment thereof, as shown by way of example only in the accompanying drawing, wherein:

FIG. 1 is a diagrammatical showing of the end portion of the head of a sewing machine having a needle bar, a needle, a presser foot and the inventive device.

FIG. 2 is a view from beneath the underside of the presser foot.

Having now reference to the accompanying drawing, and mainly to FIG. 1 thereof, a head 1 of a sewing machine will be noticed, shown only diagrammatically in its end portion since the other conventional devices are irrelevant to the ends of the invention. The shank 2 of the presser foot, the presser foot itself, generally shown at 3, the needle 10, the needle-thread 9 and the underside 4 of the presser foot, will be noticed, all of them being characteristic component parts of a sewing machine, along with the needle plate 8, also shown diagrammatically, but still understandable. By looking at FIG. 1, it will be seen that a slanting channel 5 has been formed through the presser foot, said channel having been shown in dotted lines and running through the presser foot and opening through the underside 4 thereof.

To the rear end of the presser foot 3 a small tube section 6 is affixed, which is an extension of the channel 5 and is connected to a small hose '7; the latter is fed with compressed air coming from an appropriate source, generally indicated at AC and not shown in detail.

As clearly seen in the drawing, the compressed air from AC flows through the hose 7 and, via 6 and 5, emerges from beneath the underside 4 of the foot 3 (see also FIG. 2). The tiny arrows shown between the underside of the presser foot 4 and the needle plate 8 show the compressed air stream which positively rips the needle thread 9 from beneath the presser foot underside 4. In FIG. 1 the presser foot 3 has been shown in a nearly entirely depressed position, whereas the needle 10 has been shown lifted to a certain extent; this has been done just to show that, with a total absence of mechanical devices and metal parts susceptible of obstructing the needle motion, this invention solves the subject problem once for all in an extremely simple manner without any attendant risk of breaking the needle.

Anyone skilled in the art will appreciate that the point, whatever it may be, where the needle thread 9 is driven by the compressed air stream, is in no wise critical; the

condition which is necessary and sufiicient to obtain seamlines of a good quality, without dangling threads, or, as it is usually said in the technical parlance, clean seamlines, is that the needle-thread 9 is withdrawn from beneath the underside of the presser foot and cannot be pinched between the presser foot and the fabric as the presser foot is lowered.

It is apparent that many modifications can be envisaged without departing from the scope of the invention. What has been shown is a mere example of a preferred em bodiment. For example, the compressed air feeding channel could open, in limiting conditions, also above the presser foot While still having such a direction as to rip the needle thread from beneath the underside of the presser foot. 'In limiting conditions, the air duct could even open under the needle bar and, if so, it would still succeed in ripping the needle thread from beneath the presser-foot, which is exactly the result aimed at.

In summation, the present invention has solved, for the first time, the problem of driving off the thread, by employing a directional stream of a pressurized gas, which is preferably air for reasons of economy and convenience, but could be any other gaseous fluid, Whenever quite particular processing specifications would so require.

What is claimed is:

1. In a sewing machine having a reciprocating needle, fabric supporting means disposed in the path of said needle, and a reciprocable presser foot for clamping the fabric against said supporting means and having therein anelongate needle slot open at one end, a source of compressed air, and a conduit leading from said source to said presser foot, said presser foot having a single duct extending diagonally therethrough an opening on the underface only of said presser foot at a point spaced from the inner end of saidslot and the path of reciprocation of said needle, said duct being connected to said conduit to conduct compressed air from said source directly beneath the presser foot as the presser foot descends t0 clamping position and being oriented to drive the needle-thread from beneath the presser foot before the presser foot engage the fabric.

References Cited UNITED STATES PATENTS 2,316,648 4/1943 Giglio 112218 2,424,102 7/1947 Vesconte et al. 112218 2,630,772 3/ 1953 Ederer 112-Air Digest 3,357,386 12/1967 Kalman 112-218 X 3,371,632 3/1968 Snyder etal 112-218 FOREIGN PATENTS 757,858 9/1956 Great Britain 112218' 599,677 11/1959 Italy 112- 218 H. HAMPTON HUNTER, Primary-Examiner 

